Ion transport has been deemed to be important to spermatogenesis since transferrin was first identified as a secretion product of Sertoli. Male infertility is frequently associated with disorders of iron metabolism including the disease states of hemochromatosis, congenital a atransferrinemia and severe aplastic anemia. A model for the movement of iron from serum transferrin, into Sertoli cells and then to spermatocytes and spermatids via Sertoli cell transferrin has largely been supported by experimental findings in a number of laboratories. A novel mRNA for a shortened form of transferrin was found in spermatids and named hemiferrin. The protein product of this transcript has not been described, nor the role that it might play in spermatogenesis. The experiments in this proposal address the identify, localization and molecular physiology of hemiferrin in the testis. Hemiferrin is capable of coding for nearly half of the rat transferrin molecule. Since transferrin is a tandemly duplicated gene, hemiferrin may represent the ancestral gene. The predicted sequence of hemiferrin suggests that it may function in some ways like transferrin as an ion transport protein and/or as a growth promoting factor. Experiments are designed to: a) localized hemiferrin protein in the testis, b) determine the properties of hemiferrin as related to transferrin, and c) determine the gene structure of hemiferrin.